use std::collections::HashMap;
use std::ffi::{c_void, CString};
use std::process::abort;

use cstr::cstr;
use glfw::WindowSize;

use crate::camera::Camera;
use crate::color::Color;
use crate::lighting::LightSource;
use crate::matrix::Matrix;
use crate::object::Object;
use crate::opengl::buffer::{
    ArrayKind as ArrayBufferKind,
    Buffer,
    ElementArrayKind as ElementArrayBufferKind,
    Usage as BufferUsage,
};
use crate::opengl::currently_bound::CurrentlyBound;
#[cfg(feature = "debug")]
use crate::opengl::debug::{MessageSeverity, MessageSource, MessageType};
use crate::opengl::shader::{
    Error as GlShaderError,
    Program as GlShaderProgram,
    Shader as GlShader,
};
use crate::opengl::texture::{set_active_texture_unit, TextureUnit};
use crate::opengl::vertex_array::{PrimitiveKind, VertexArray};
use crate::opengl::{clear_buffers, enable, BufferClearMask, Capability};
use crate::projection::new_perspective;
use crate::shader::Program as ShaderProgram;
use crate::vector::{Vec2, Vec3};
use crate::vertex::Vertex;

#[derive(Debug)]
pub struct Renderer<CameraT>
{
    camera: CameraT,
    shader_programs: HashMap<u64, GlShaderProgram>,
}

impl<CameraT> Renderer<CameraT>
where
    CameraT: Camera,
{
    pub fn new(window: &glfw::Window, camera: CameraT) -> Result<Self, Error>
    {
        gl::load_with(|symbol| {
            let proc_name = unsafe { CString::from_vec_unchecked(symbol.into()) };

            match window.get_proc_address(proc_name.as_c_str()) {
                Ok(addr) => addr as *const c_void,
                Err(err) => {
                    println!(
                        "FATAL ERROR: Failed to get adress of OpenGL function {}. {}",
                        symbol, err
                    );

                    abort();
                }
            }
        });

        #[cfg(feature = "debug")]
        Self::initialize_debug();

        let window_size = window.size().map_err(Error::GetWindowSizeFailed)?;

        Self::set_viewport(&Vec2 { x: 0, y: 0 }, &window_size);

        enable(Capability::DepthTest);

        Ok(Self {
            camera,
            shader_programs: HashMap::new(),
        })
    }

    pub fn create_shader_programs<'program>(
        &mut self,
        programs: impl IntoIterator<Item = &'program ShaderProgram>,
    ) -> Result<(), Error>
    {
        for program in programs {
            let gl_shaders = program
                .shaders()
                .iter()
                .map(|shader| {
                    let gl_shader = GlShader::new(shader.kind());

                    gl_shader.set_source(shader.source())?;
                    gl_shader.compile()?;

                    Ok::<_, Error>(gl_shader)
                })
                .collect::<Result<Vec<_>, _>>()?;

            let gl_shader_program = GlShaderProgram::new();

            for gl_shader in &gl_shaders {
                gl_shader_program.attach(gl_shader);
            }

            gl_shader_program.link()?;

            self.shader_programs
                .insert(program.u64_hash(), gl_shader_program);
        }

        Ok(())
    }

    pub fn render<'obj>(
        &self,
        objects: impl IntoIterator<Item = &'obj Object>,
        light_source: Option<&LightSource>,
        window_size: &WindowSize,
    ) -> Result<(), Error>
    {
        clear_buffers(BufferClearMask::COLOR | BufferClearMask::DEPTH);

        for obj in objects {
            let shader_program = self
                .shader_programs
                .get(&obj.shader().u64_hash())
                .ok_or(Error::MissingShaderProgram)?;

            shader_program.activate(|shader_program_curr_bound| {
                apply_transformation_matrices(
                    obj,
                    shader_program,
                    &self.camera,
                    window_size,
                    &shader_program_curr_bound,
                );

                apply_light(
                    obj,
                    shader_program,
                    light_source,
                    &self.camera,
                    &shader_program_curr_bound,
                );

                for (texture_id, texture) in obj.textures() {
                    let texture_unit = TextureUnit::from_texture_id(*texture_id)
                        .ok_or(Error::TextureIdIsInvalidTextureUnit)?;

                    set_active_texture_unit(texture_unit);

                    texture.inner().bind(|_| {});
                }

                Self::draw_object(obj);

                Ok::<_, Error>(())
            })?;
        }

        Ok(())
    }

    pub fn set_viewport(position: &Vec2<u32>, size: &WindowSize)
    {
        crate::opengl::set_viewport(position, size);
    }

    #[must_use]
    pub fn camera(&self) -> &CameraT
    {
        &self.camera
    }

    pub fn camera_mut(&mut self) -> &mut CameraT
    {
        &mut self.camera
    }

    #[cfg(feature = "debug")]
    fn initialize_debug()
    {
        use crate::opengl::debug::{
            enable_debug_output,
            set_debug_message_callback,
            set_debug_message_control,
            MessageIdsAction,
        };

        enable_debug_output();

        set_debug_message_callback(opengl_debug_message_cb);

        set_debug_message_control(None, None, None, &[], MessageIdsAction::Disable);
    }

    fn draw_object(obj: &Object)
    {
        // TODO: Creating a new vertex buffer each draw is really dumb and slow this
        // should be rethinked
        let renderable = Renderable::new(obj.mesh().vertices(), obj.mesh().indices());

        renderable.vertex_arr.bind(|vert_arr_curr_bound| {
            if let Some(index_info) = &renderable.index_info {
                VertexArray::draw_elements(
                    &vert_arr_curr_bound,
                    PrimitiveKind::Triangles,
                    0,
                    index_info.cnt,
                );
            } else {
                VertexArray::draw_arrays(
                    &vert_arr_curr_bound,
                    PrimitiveKind::Triangles,
                    0,
                    3,
                );
            }
        });
    }
}

#[derive(Debug)]
pub struct Renderable
{
    vertex_arr: VertexArray,

    /// Vertex and index buffer has to live as long as the vertex array
    _vertex_buffer: Buffer<Vertex, ArrayBufferKind>,
    index_info: Option<IndexInfo>,
}

impl Renderable
{
    pub fn new(vertices: &[Vertex], indices: Option<&[u32]>) -> Self
    {
        let vertex_arr = VertexArray::new();
        let vertex_buffer = Buffer::new();

        let mut index_info = None;

        vertex_arr.bind(|vert_arr_curr_bound| {
            vertex_buffer.bind(|vert_buf_curr_bound| {
                Buffer::store(&vert_buf_curr_bound, vertices, BufferUsage::Static);

                VertexArray::configure_attrs(&vert_arr_curr_bound, &vert_buf_curr_bound);
            });

            if let Some(indices) = indices {
                let new_index_buffer = Buffer::new();

                new_index_buffer.bind(|index_buf_curr_bound| {
                    Buffer::store(&index_buf_curr_bound, indices, BufferUsage::Static);
                });

                index_info = Some(IndexInfo {
                    _buffer: new_index_buffer,
                    cnt: indices.len().try_into().unwrap(),
                });
            }
        });

        Self {
            vertex_arr,
            _vertex_buffer: vertex_buffer,
            index_info,
        }
    }
}

/// Renderer error.
#[derive(Debug, thiserror::Error)]
pub enum Error
{
    #[error("Failed to get window size")]
    GetWindowSizeFailed(#[source] glfw::Error),

    #[error("Texture ID is a invalid texture unit")]
    TextureIdIsInvalidTextureUnit,

    #[error(transparent)]
    GlShader(#[from] GlShaderError),

    #[error("No shader program object was found for object")]
    MissingShaderProgram,
}

fn apply_transformation_matrices(
    object: &Object,
    gl_shader_program: &GlShaderProgram,
    camera: &impl Camera,
    window_size: &WindowSize,
    shader_program_curr_bound: &CurrentlyBound<GlShaderProgram>,
)
{
    gl_shader_program.set_uniform_matrix_4fv(
        shader_program_curr_bound,
        cstr!("model"),
        &object.transform().as_matrix(),
    );

    let view = create_view(camera);

    gl_shader_program.set_uniform_matrix_4fv(
        shader_program_curr_bound,
        cstr!("view"),
        &view,
    );

    #[allow(clippy::cast_precision_loss)]
    let projection = new_perspective(
        80.0f32.to_radians(),
        window_size.width as f32 / window_size.height as f32,
        100.0,
        0.1,
    );

    gl_shader_program.set_uniform_matrix_4fv(
        shader_program_curr_bound,
        cstr!("projection"),
        &projection,
    );
}

fn apply_light(
    obj: &Object,
    gl_shader_program: &GlShaderProgram,
    light_source: Option<&LightSource>,
    camera: &impl Camera,
    shader_program_curr_bound: &CurrentlyBound<GlShaderProgram>,
)
{
    gl_shader_program.set_uniform_vec_3fv(
        shader_program_curr_bound,
        cstr!("light.position"),
        &light_source.map_or_else(Vec3::default, |light_source| {
            light_source.position().clone()
        }),
    );

    gl_shader_program.set_uniform_vec_3fv(
        shader_program_curr_bound,
        cstr!("light.ambient"),
        &light_source
            .map_or(Color::WHITE_F32, |light_source| {
                light_source.ambient().clone()
            })
            .into(),
    );

    gl_shader_program.set_uniform_vec_3fv(
        shader_program_curr_bound,
        cstr!("light.diffuse"),
        &light_source
            .map_or(Color::WHITE_F32, |light_source| {
                light_source.diffuse().clone()
            })
            .into(),
    );

    gl_shader_program.set_uniform_vec_3fv(
        shader_program_curr_bound,
        cstr!("light.specular"),
        &light_source
            .map_or(Color::WHITE_F32, |light_source| {
                light_source.specular().clone()
            })
            .into(),
    );

    #[allow(clippy::cast_possible_wrap)]
    gl_shader_program.set_uniform_1i(
        shader_program_curr_bound,
        cstr!("material.ambient"),
        obj.material().ambient_map().into_inner() as i32,
    );

    #[allow(clippy::cast_possible_wrap)]
    gl_shader_program.set_uniform_1i(
        shader_program_curr_bound,
        cstr!("material.diffuse"),
        obj.material().diffuse_map().into_inner() as i32,
    );

    #[allow(clippy::cast_possible_wrap)]
    gl_shader_program.set_uniform_1i(
        shader_program_curr_bound,
        cstr!("material.specular"),
        obj.material().specular_map().into_inner() as i32,
    );

    gl_shader_program.set_uniform_1fv(
        shader_program_curr_bound,
        cstr!("material.shininess"),
        obj.material().shininess(),
    );

    gl_shader_program.set_uniform_vec_3fv(
        shader_program_curr_bound,
        cstr!("view_pos"),
        &camera.position(),
    );
}

fn create_view(camera: &impl Camera) -> Matrix<f32, 4, 4>
{
    let mut view = Matrix::new();

    view.look_at(&camera.position(), &camera.target(), &camera.global_up());

    view
}

#[cfg(feature = "debug")]
#[tracing::instrument(skip_all)]
fn opengl_debug_message_cb(
    source: MessageSource,
    ty: MessageType,
    id: u32,
    severity: MessageSeverity,
    message: &str,
)
{
    use std::backtrace::{Backtrace, BacktraceStatus};

    use tracing::{event, Level};

    macro_rules! create_event {
        ($level: expr) => {
            event!($level, ?source, ?ty, id, ?severity, message);
        };
    }

    if matches!(severity, MessageSeverity::Notification) {
        return;
    }

    match ty {
        MessageType::Error => {
            create_event!(Level::ERROR);

            let backtrace = Backtrace::capture();

            if matches!(backtrace.status(), BacktraceStatus::Captured) {
                event!(Level::TRACE, "{backtrace}");
            }
        }
        MessageType::Other => {
            create_event!(Level::INFO);
        }
        _ => {
            create_event!(Level::WARN);
        }
    };
}

#[derive(Debug)]
struct IndexInfo
{
    _buffer: Buffer<u32, ElementArrayBufferKind>,
    cnt: u32,
}